CN107849723B

CN107849723B - Culinary article comprising a rare earth oxide layer

Info

Publication number: CN107849723B
Application number: CN201680043020.4A
Authority: CN
Inventors: 杰罗姆·波莱塞尔·玛丽斯; 劳伦特·卡莉耶; 奥里莱恩·迪邦谢
Original assignee: SEB SA
Current assignee: SEB SA
Priority date: 2015-07-21
Filing date: 2016-07-19
Publication date: 2020-11-20
Anticipated expiration: 2036-07-19
Also published as: EP3325694A1; FR3039053A1; CN107849723A; KR20180033219A; US20180171481A1; FR3039053B1; KR102470075B1; ES2786299T3; US10815571B2; WO2017013351A1; EP3325694B1

Abstract

The present invention generally relates to a culinary article having a surface provided with a coating comprising at least one rare earth oxide layer. The coating not only has mechanical hardness and wear resistance characteristics equivalent to those of enamel and ceramics, but also has excellent inherent hydrophobicity, so that the obtained coating has non-adhesiveness equivalent to that of fluorocarbon coating and is suitable for cooking application.

Description

Culinary article comprising a rare earth oxide layer

The present invention relates generally to a culinary article having on at least one surface a coating comprising at least one rare earth oxide layer.

Currently, the various coatings used for food cooking each present basic performance characteristics according to their nature, which vary according to the nature of the coating.

Thus, fluorocarbon resin-based coatings, such as Polytetrafluoroethylene (PTFE) resin coatings, exhibit excellent non-stick properties, while coatings based on enamels or sol-gels (commonly known as ceramics) exhibit excellent material hardness and high temperature resistance (especially over 400 ℃).

However, at present, no coating exists that combines these properties, or at least does not exist in an optimal manner.

To some extent, fluorocarbon resin based non-stick coatings are formed, for example, by adding fillers (e.g., SiO) to the formulation₂、TiO₂、Al₂O₃SiC, BN, diamond, etc.) can improve their wear, scratch and spallation resistance (delamination), but do not achieve the mechanical properties of enamel or sol-gel coatings.

To some extent, the sol-gel coating can improve non-tackiness, for example by introducing a polydimethylsiloxane-type lubricity additive, but not as far as the non-tackiness of fluorocarbon resin-based coatings. As regards the enamel-based coating, its non-stick properties continue to be low, whatever the known technical solutions applied. To solve this problem, the applicant has developed a coating comprising at least one layer of rare earth oxide having not only mechanical hardness and abrasion resistance characteristics similar to those of enamels and ceramics, but also excellent intrinsic hydrophobicity, giving the resulting coating non-tackiness comparable to that of fluorocarbon resin-based coatings and suitable for culinary applications.

The use of rare earth oxides for ceramic coatings is known to those skilled in the art. Thus, patent document FR 2925063 describes a ceramic layer rich in rare earth oxides for use in the field of capacitors or steam turbines. This document describes a metal substrate covered in such a way that it comprises a primary oxide and a secondary oxide. The primary oxide comprises cerium and hafnium and the secondary oxide comprises secondary oxide cations selected from rare earth, yttrium and scandium cations.

The coating described in document FR 2925063 results in a ceramic material having relatively high liquid-repellent properties, such as water repellency.

The invention therefore relates to a culinary article comprising a support having an inner surface able to contain food and an outer surface intended to be arranged facing a heat source, and a coating applied on at least one of the two surfaces, characterized in that the coating comprises at least one continuous or discontinuous layer of rare earth oxide comprising at least one rare earth oxide matrix.

According to an advantageous alternative of the invention, the rare earth oxide matrix may comprise at least one oxide of the lanthanide series.

According to another advantageous alternative, the rare earth oxide matrix may comprise cerium oxide alone or in mixture with at least one other lanthanide oxide.

The addition of cerium oxide to the rare earth oxide matrix will provide a rare earth oxide layer barrier effect (corrosion resistance, oxidation resistance, impermeability to liquids and gases).

This barrier effect is due to the hydrophobic nature of cerium oxide (commonly known as ceria), in particular to make it water-insoluble.

Advantageously, the rare earth oxide layer may also comprise a filler dispersed in the matrix, said filler being selected from the group consisting of fluorocarbon resins, Polyetheretherketones (PEEK), Polyetherketones (PEK), Polyimides (PI), polyamide-imides (PAI), Polyethersulfones (PES), polyphenylene sulfides (PPS), silicone beads, and mixtures thereof.

Such additions ameliorate, or even eliminate, the problems associated with cracking of the lanthanide oxide layer resulting from mechanical energy dissipation. The additive does not change the hydrophobicity of the rare earth oxide layer.

Preferably, the filler may comprise a fluorocarbon resin selected from the group consisting of: PTFE, modified PTFE, tetrafluoroethylene and perfluoropropyl vinyl ether copolymer (PFA), tetrafluoroethylene and hexafluoropropylene copolymer (FEP), and mixtures thereof.

In the context of the present invention, the filler may preferably be present in a content of between 0.1 and 50% by weight relative to the total dry weight of the rare earth oxide layer. The filler content should not exceed 50 wt% in order to maintain the physicochemical properties of the cerium oxide.

Advantageously, the thickness of the rare earth oxide layer may be between 0.1 and 50 μm. It should be noted that the thickness of the rare earth oxide layer may vary depending on the application method used.

In addition, the filler is preferably non-porous. In fact, if the filler is porous, especially in the case of a fluorine-free filler, the non-stick properties of the coating will be reduced.

Preferably, the surface of the rare earth oxide layer may be structured or textured.

The structuring of the surface of the rare earth oxide layer will advantageously reduce the wettability of said surface of the rare earth oxide layer and thus obtain a superhydrophobic rare earth oxide layer.

In the context of the present invention, the term superhydrophobic layer means a surface having a contact angle of a water droplet of more than 150 °.

In the context of the present invention, the term structured or textured surface means a surface characterized by relief or a controlled roughness.

Advantageously, the support is made of metal, glass, ceramic, china clay (terra cuite) or a plastic material.

Preferably, the carrier may be metal and made of anodized or unanodized aluminum or aluminum alloy, optionally polished (polar), wire-drawn (broser), sanded (sabler) or sandblasted (microballer), or made of steel, optionally polished, wire-drawn, sanded or sandblasted, or made of stainless steel, optionally polished, wire-drawn, sanded or sandblasted, or made of cast steel, cast aluminum, cast iron or copper, optionally forged or polished.

Preferably, the support may be a metal and may comprise alternating layers of metal and/or metal alloy, or a cap (alloy) of cast aluminium, aluminium or aluminium alloy reinforced by a stainless steel outer base material.

According to one embodiment of the invention, the coating may also comprise at least one layer arranged on the rare earth oxide layer, said layer comprising at least one fluorocarbon resin alone or together with a thermally stable binder resin resistant to temperatures of 200 ℃, the resin or resins forming a continuous sintered network.

Advantageously, in this embodiment, the fluorocarbon resin may be selected from PTFE, modified PTFE, tetrafluoroethylene and perfluoropropyl vinyl ether copolymer (PFA), tetrafluoroethylene and hexafluoropropylene copolymer (FEP), and mixtures thereof.

Preferably, in this embodiment, the binder resin may be selected from polyamide-imide (PAI), Polyetherimide (PEI), Polyamide (PI), Polyetherketone (PEK), Polyetheretherketone (PEEK), Polyethersulfone (PES), polyphenylene sulfide (PPS), and mixtures thereof.

These binder resins have the advantage of being heat resistant and able to withstand temperatures in excess of 200 ℃.

As non-limiting examples of cooking products of the invention, mention may in particular be made of cooking products such as pots or pans, woks, frying pans, porridge pots, grills, baking moulds and baking plates, as well as barbecue grills and grills.

The culinary article of the invention may be prepared according to any suitable method known to those skilled in the art. In particular, the rare earth oxide layer may be applied using a pyrolytic spray, a thermal spray, a PVD (physical vapor deposition) method, a sol-gel method, or using an electrochemical method or a sintering method.

It should be noted that the raw materials used for the rare earth oxide layer application may take one of two forms:

rare earth oxide powders, pure or mixed with other materials in powder form; or

-a colloidal rare earth oxide dispersion stable in an aqueous or solute medium; or

A precursor solution of a rare earth salt in water, ethanol or an ester, such as a nitrate, acetate, acetylacetonate, hydrochloride or ammonium salt.

The precursor solution may additionally also comprise one or more additives. In particular, the additive or additives may be an acid such as acetic acid, citric acid or tartaric acid. These acids are used as complexing agents for salt precursors, in particular rare earth salt precursors. The introduction of this additive in the precursor solution may thus enable a homogeneous and dense network of rare earth oxides to be obtained, thus limiting the formation of pores in the matrix of the layer.

Pyrolysis spray application comprises spraying or misting droplets of a rare earth salt precursor solution onto at least one surface of a culinary article maintained at an elevated temperature, preferably in excess of 350 ℃. The surface temperature of the article is maintained at a threshold value to allow pyrolysis of the rare earth salt prior to contact with the surface, thereby producing rare earth oxide adhered to the surface in the form of nanoparticles. The pyrolytic spray deposition makes it possible to obtain a rare earth oxide layer by additive effect.

Post-firing the article at a higher temperature than that used to deposit the layer may improve the crystallinity and density of the rare earth oxide layer (e.g., post-firing may be performed at a temperature above 400 ℃).

The thermal spray application (or thermal spray) is carried out at a temperature that enables the rare earth oxide to melt, either in the form of a pure rare earth oxide powder or mixed with other powder materials, or in the form of a rare earth salt precursor solution.

In the case where the starting compound is in the form of a rare earth oxide fine powder, it is injected as close to the flame or torch as possible. The core temperature (ideally >2500 ℃) allows for the continuous flow of molten oxide powder particles, combustible or ionized gas, while refueling the torch, to initiate a spray with sufficient kinetic energy to spray the molten particles onto the surface of the culinary article and bind them to the article, thereby gradually forming a dense layer.

Instead of powders, the starting compounds in the form of rare earth salt precursor solutions can also be injected into a plasma torch or flame spray gun, but in a region with a lower temperature to initiate pyrolysis of the rare earth salts and inject them onto the surface of the culinary article to produce a rare earth oxide layer. For atmospheric plasma torches, oxidation may be induced by ambient oxygen.

In the context of the present invention, the thermal spray application (or thermal spray) may be by using, for example, argon/hydrogen Ar-H₂Plasma torch of the type ionizing a carrier gas composition, or flame or HVOF type spraying using an oxidizer/fuel gas composition of the oxygen/acetylene type.

For example, the thermal spray plasma torch produces a flame core temperature of approximately 15,000 ℃. During the thermal spray, the surface of the culinary article is maintained at a temperature of 200 ℃ to 350 ℃ to improve the spreading and adhesion kinetics of the molten oxide particles upon collision with its surface. Thus, a layer of several micrometers or several tens of micrometers can be formed by the accumulation action.

Advantageously, as described above, the filler may be dispersed in the rare earth oxide layer. These fillers can be introduced in particular in the form of a dispersion of polymeric particles (in a rare-earth salt precursor solution) or in the form of a dry powder (in a rare-earth salt precursor solution or in a powder comprising a rare-earth oxide).

In case the starting compound comprises a filler, the procedure of application of the rare earth oxide layer should be optimized so as not to cause total thermal degradation of the filler during application.

Advantageously, as described above, the rare earth oxide layer may be structured (or textured). This structuring can be obtained by stamping the support surface of the culinary article, chemically or physically etching the support surface of the culinary article previously covered with a resin, preferably photocurable, having the desired transferred pattern.

Examples

Example 1: pyrolysis spray preparation and application of cerium oxide layer

The precursor composition was prepared as follows:

cerium acetate (Ce (OOCCH)₃)₃·H₂O) is diluted in a mixture of water and ethanol with the volume concentration ratio of 70: 30.

After that, the solution was stirred at room temperature for 36 hours to obtain a precipitate-free transparent solution having a cerium concentration of 0.02 mol/L.

The composition was sprayed multiple times onto the surface of a stainless steel sample using a pyrolytic spray. The spraying is carried out using a spray gun or atomizer and the sample is brought to a distance of about 20cm from the spray gun or atomizer, the surface of the sample being maintained at a temperature exceeding 350 ℃ to crystallize the cerium oxide deposit in solid form on the surface of the sample.

10 to 20 spray cycles form a submicron thickness layer of solid rare earth oxide between 100 and 400nm thick.

Example 2: pyrolysis spray preparation and application of cerium oxide layer

The same procedure as described in example 1 was followed by adding L-proline as a chelating agent to cerium (III) nitrate hexahydrate (Ce (NO) in a molar ratio of 1:1₃)₃·6H₂O) preparation of the precursor composition and application of the rare earth oxide layer.

Example 3: pyrolysis spray preparation and application of cerium oxide layer

By diluting cerium (III) chloride heptahydrate in a 3:1 molar ratio water/ethanol mixture

(CeCl₃·7H₂O) to obtain a cerium concentration ranging between 0.05 and 0.025 mol/L.

In this example, spray deposition was achieved on the surface of a glass sample maintained at 400 ℃ according to the same method described in example 1, to obtain a continuous and homogeneous layer of rare earth oxide.

Example 4: preparation and application of thermal spraying (or thermal spraying) of cerium oxide layer

The precursor composition was prepared as follows:

75g of cerium (III) nitrate hexahydrate (Ce (NO)₃)₃·6H₂O) was dissolved in 1.5 l of pure water;

after that the solution was stirred for 20 minutes.

The precursor composition is then assisted with a carrier gas (Ar-H)₂Mixture type) stream was injected in a plasma torch parameterized to enable pyrolysis of the cerium salt before contacting the surface of the aluminum sample.

The cerium thus atomized is oxidized on the surface in the form of cerium oxide. A cerium oxide layer is thus prepared on the surface of the sample by the cumulative effect.

Example 5: preparation and use of thermal spray application of cerium oxide layer comprising fluoropolymer filler

The powder is prepared by mixing cerium oxide powder having a particle size ranging from 30 to 70 micrometers and PTFE powder (or PFA) having a particle size ranging from 10 to 50 micrometers.

The powder is then passed through a carrier gas stream (Ar-H)₂Mixture type) was injected in a plasma torch, which was parameterized to enable the cerium oxide to be pyrolyzed before contacting the surface of the aluminum sample. The spray distance of the torch from the sample surface was about 125mm and the powder was ejected from the plasma torch at a linear displacement speed of about 75 m/min.

The surface of the sample on which the powder was applied was maintained at a temperature of 300 ℃ to improve diffusion kinetics of the molten cerium oxide particles and homogeneity of the rare earth oxide layer comprising PTFE (or PFA) particles.

The thickness of the generated rare earth oxide layer reaches dozens of microns

Example 6: preparation and application of a cerium oxide layer on a structured sample by PVD

The superhydrophobic rare earth oxide layer is generated in two successive steps:

1) texturing the surface of an aluminum-based metal sample; then the

2) A hydrophobic cerium oxide layer was deposited by PVD onto the textured surface of the sample.

Step 1) there are many possible variations of the texturing step.

For example, a first variant consists in texturing the sample surface by chemical etching of the surface (deposition of a photocurable resin/irradiation through a suitable mask/treatment of the unexposed areas with a solvent to produce the design elements to be transferred) resulting in the formation of textured areas on the sample surface.

The pattern depth can be controlled by the etching time. The textured regions were 9 μm wide, 11 μm apart from each other and had a depth of 15 μm.

A second variation includes randomly texturing the sample surface using chemical etching.

In this variant of embodiment, the surface of the aluminium sample is randomly exposed to an acid to obtain the following roughness characteristics:

-5 μm Ra of the particles,

-5 μm Rq, and

-25 μm Rz.

A third embodiment variant involves stamping the sample surface using a textured stencil.

In this variant, the sample surface is textured under pressure using a hard texturing master made of titanium nitride. The transferred textured regions were 9 μm wide, 11 μm apart from each other and had a depth of 15 μm.

Step 2) comprises depositing a continuous layer of cerium oxide on the textured surface using PVD techniques. The deposition was performed under vacuum using a sintered ceria target.

The resulting layer has a thickness between 50nm (on the second deformed randomly textured surface) and 500nm (on the first and third deformed patterned surfaces) and accurately transfers the textured topography.

Example 7: preparation and application of a cerium oxide layer by the sol-gel method (alcoholate)

Mixing cerium butoxide with 2-butanol with the molar ratio of 0.1; acetylacetone, which was used as a chelating agent, was then added to the mixture.

Then, an aqueous hydrochloric acid solution having a concentration of 1mol/L was added dropwise with stirring (note that the molar ratio of cerium butoxide/acetylacetone was 2, and the molar ratio of cerium butoxide/water was 0.5), and the resulting sol was stirred for 48 hours to achieve an appropriate balance of hydrolysis and condensation reactions.

Then an inorganic black pigment consisting of copper chromium oxide and iron was added at 5% by weight relative to the total weight of the solution, and finally an alpha-alumina filler was introduced to 4% by weight relative to the total weight of the solution with stirring.

In this embodiment, the cerium oxide layer is formed by a sol-gel method using hydrolysis/condensation of cerium butoxide.

For this purpose, the solution obtained as described above was sprayed onto the surface of an aluminum sample that had been previously ground and degreased, the surface of the sample having been heated to a temperature of 60 to 80 ℃ to prevent dripping and to discharge a part of the solvent during the coating process.

In order to obtain a sufficient layer thickness while minimizing the risk of cracking, the initial layer was subjected to a drying process at 80 ℃ for 5 minutes before spraying a second layer of the same sol-gel solution onto the sample.

The rare earth oxide layer was subjected to a 10 minute pre-bake step at 120 ℃ to evaporate most of the solvent.

Finally, the entire sample and the rare earth oxide layer were heat treated at 350 ℃ to densify the ceria network.

The resulting rare earth oxide layer had a thickness of 15 μm, and no visible cracks were observed using a binocular microscope.

Example 8: preparation and application of rare earth oxide layers comprising fluoropolymer fillers using sol-gel (alkoxide) method

PTFE powder was added to the sol-gel solution of example 7 until 2 wt% of the total weight of the solution. The cerium layer was then applied using the sol gel method via hydrolysis/condensation of cerium butoxide, as described in example 7.

It should be noted that these PTFE particles serve to enhance the hydrophobicity and non-tackiness of the rare earth oxide layer.

Example 9: preparation and application of rare earth oxide layers comprising fluoropolymer fillers using sol-gel (salt) method

Cerium nitrate was dissolved in deionized water to obtain a concentration of 1mol/L, and then citric acid of 99.5% purity grade was added with stirring, wherein the molar ratio of cerium nitrate/citric acid was 0.5.

The solution was stirred at room temperature for 1 hour, then a mixture of isopropanol and PTFE powder (mass ratio 48/2) was added to the solution at a volume ratio of 1:1 to improve the service life of the sol and to introduce fluorinated fillers to improve the hydrophobicity of the coating.

Finally, the solution was stirred for 24 hours to obtain a stable and translucent sol.

The resulting solution was then sprayed to obtain a rare earth oxide layer on the surface of a previously degreased smooth aluminum sample, which was heated to 40 to 60 ℃ to avoid dripping and to drain a portion of the solvent during application.

After initial drying at 100 ℃ for 10 minutes, the aluminum sample was heat treated at 380 ℃ for 30 minutes to densify the ceria mesh.

A 500nm thick cerium oxide layer was obtained.

Example 10: preparation and application of cerium oxide layer by using electrochemical method and sintering method

A previously degreased smooth aluminum sample was placed on the negative electrode of the electrochemical deposition system.

Ammonia NH at 5% volume concentration₃In the presence of (2) a precursor Ce (NO)₃)₃-6H₂O was added to the aqueous solution (0.1 mol/L).

By applying a potential of 3V to the electrochemical deposition system, a cerium hydroxide-based rare earth oxide layer was formed after 1 hour.

Finally, the amorphous cerium hydroxide-based rare earth oxide layer was oxidized at 550 ℃ for 5 hours in air to produce a 0.5 μm thick cerium oxide film.

Results of the tests conducted

Hydrophobicity testing of the resulting coatings

The hydrophobic properties of the coatings obtained according to the previous examples were tested by measuring the contact angle of a water drop on the coating using a GBX Digidrop goniometer. The measurement results are shown in the following table.

Claims

1. A cooking article comprising a support having an inner surface capable of containing food and an outer surface intended to be arranged towards a heat source, and a coating applied on at least one of said two surfaces,

the culinary article is characterized in that the coating comprises at least one layer of a superhydrophobic rare earth oxide comprising at least one rare earth oxide matrix,

wherein the superhydrophobic rare earth oxide layer additionally comprises a filler dispersed in the matrix, the filler selected from the group consisting of fluorocarbon resin, Polyetheretherketone (PEEK), Polyetherketone (PEK), Polyimide (PI), polyamide-imide (PAI), Polyethersulfone (PES), polyphenylene sulfide (PPS), silicone beads, and mixtures thereof.

2. The culinary article of claim 1, wherein the matrix comprises at least one lanthanide oxide.

3. The culinary article of any preceding claim, wherein the substrate comprises cerium oxide alone, or a mixture of cerium oxide and at least one other lanthanide oxide.

4. The culinary article of claim 1, wherein the filler comprises a fluorocarbon resin selected from Polytetrafluoroethylene (PTFE), modified PTFE, copolymers of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA), copolymers of tetrafluoroethylene and hexafluoropropylene (FEP), and mixtures thereof.

5. The culinary article of any of claims 1 and 4, wherein filler is present in an amount of 0.1 to 50 wt% relative to the total dry weight of the rare earth oxide layer.

6. The culinary article of claim 1, wherein the rare earth oxide layer is between 0.1 and 50 μ ι η thick.

7. The culinary article of any of claims 1 and 6, wherein the rare earth oxide layer is structured.

8. The culinary article of claim 1, wherein the carrier is made of a metal, glass, ceramic, clay, or plastic material.

9. The culinary article of claim 8, wherein the carrier is a metal and is made of anodized or unanodized aluminum or an aluminum alloy, optionally polished, wire-drawn, sanded or grit-blasted, or of steel, optionally polished, wire-drawn, grit-blasted or grit-blasted, or of stainless steel, optionally polished, wire-drawn, grit-blasted or grit-blasted, or of cast steel, cast aluminum, cast iron or copper, optionally forged or polished.

10. The culinary article of claim 8, wherein the carrier is made of metal and comprises alternating layers of metal and/or metal alloy or a cap of cast aluminum, or aluminum alloy reinforced with a stainless steel outer base material.

11. The culinary article of claim 1, wherein the coating additionally comprises at least one layer disposed on the rare earth oxide layer, the layer comprising at least one fluorocarbon resin alone or mixed with a thermally stable binder resin resistant to temperatures in excess of 200 ℃, the resin or resins constituting a continuous sintered network.

12. The culinary article of claim 11, wherein the fluorocarbon resin is selected from Polytetrafluoroethylene (PTFE), modified PTFE, copolymers of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA), copolymers of tetrafluoroethylene and hexafluoropropylene (FEP), and mixtures thereof.

13. The culinary article of any of claims 11 and 12, wherein the adhesive resin is selected from polyamide-imide (PAI), Polyetherimide (PEI), Polyamide (PI), Polyetherketone (PEK), Polyetheretherketone (PEEK), Polyethersulfone (PES), polyphenylene sulfide (PPS), and mixtures thereof.